diff --git a/app/Livewire/Admin/EditInvoiceSeries.php b/app/Livewire/Admin/EditInvoiceSeries.php
new file mode 100644
index 0000000..eed4209
--- /dev/null
+++ b/app/Livewire/Admin/EditInvoiceSeries.php
@@ -0,0 +1,123 @@
+<?php
+
+namespace App\Livewire\Admin;
+
+use App\Models\InvoiceSeries;
+use Illuminate\Validation\Rule;
+use LivewireUI\Modal\ModalComponent;
+
+/**
+ * Editing a Rechnungskreis, with the parts that cannot move held still.
+ *
+ * The same shape as EditDatacenter and for the same reason: some fields stop
+ * being editable once something depends on them. Here the something is a
+ * document in somebody's accounts.
+ *
+ * The prefix is part of every number already issued. Changing it from RE to AR
+ * does not rename anything — it leaves a series whose documents say RE-2026-…
+ * and whose next document says AR-2026-…, with no record that they belong
+ * together. Free while the series is empty, which is the case that matters: a
+ * prefix chosen wrongly on the day the shop opens.
+ *
+ * The counter may be raised but never lowered. Lowering it re-issues a number
+ * that is already printed on a document somebody holds, and gapless-and-
+ * ascending is a legal requirement rather than a preference.
+ */
+class EditInvoiceSeries extends ModalComponent
+{
+    public string $uuid = '';
+
+    public string $name = '';
+
+    public string $prefix = '';
+
+    public int $digits = 4;
+
+    public bool $yearlyReset = true;
+
+    public int $nextNumber = 1;
+
+    public bool $active = true;
+
+    /** How many documents this series has already issued. */
+    public int $issued = 0;
+
+    /** The lowest number this counter may still be set to. */
+    public int $floor = 1;
+
+    public function mount(string $uuid): void
+    {
+        $this->authorize('site.manage'); // modals are reachable without the route middleware
+
+        $series = InvoiceSeries::query()->where('uuid', $uuid)->firstOrFail();
+
+        $this->uuid = $uuid;
+        $this->name = $series->name;
+        $this->prefix = $series->prefix;
+        $this->digits = (int) $series->digits;
+        $this->yearlyReset = (bool) $series->yearly_reset;
+        $this->nextNumber = (int) $series->next_number;
+        $this->active = (bool) $series->active;
+        $this->issued = $series->invoices()->count();
+        $this->floor = (int) $series->next_number;
+    }
+
+    public function save()
+    {
+        $this->authorize('site.manage');
+
+        $series = InvoiceSeries::query()->where('uuid', $this->uuid)->firstOrFail();
+
+        // Recomputed from the database, never read back from the properties the
+        // browser returns: these two rules are what keep already-issued numbers
+        // from being re-used, and a forged field must not lift either.
+        $issued = $series->invoices()->count();
+        $floor = (int) $series->next_number;
+
+        $rules = [
+            'name' => 'required|string|max:120',
+            'digits' => 'required|integer|min:3|max:10',
+            'active' => 'boolean',
+            'nextNumber' => ['required', 'integer', 'min:'.$floor],
+        ];
+
+        if ($issued === 0) {
+            $rules['prefix'] = [
+                'required', 'string', 'max:12', 'regex:/^[A-Z0-9-]+$/',
+                Rule::unique('invoice_series', 'prefix')->ignore($series->id),
+            ];
+            // Only while nothing has been issued: switching an established
+            // series between yearly and continuous puts a gap in one of them.
+            $rules['yearlyReset'] = 'boolean';
+        }
+
+        if ($issued === 0) {
+            $this->prefix = strtoupper(trim($this->prefix));
+        } else {
+            $this->prefix = $series->prefix;
+            $this->yearlyReset = (bool) $series->yearly_reset;
+        }
+
+        $data = $this->validate($rules);
+
+        $series->update([
+            'name' => $data['name'],
+            'digits' => $data['digits'],
+            'next_number' => $data['nextNumber'],
+            'active' => $data['active'],
+            ...($issued === 0 ? [
+                'prefix' => $data['prefix'],
+                'yearly_reset' => $data['yearlyReset'],
+            ] : []),
+        ]);
+
+        $this->dispatch('notify', message: __('finance.series_saved'));
+
+        return $this->redirectRoute('admin.finance', navigate: true);
+    }
+
+    public function render()
+    {
+        return view('livewire.admin.edit-invoice-series');
+    }
+}
diff --git a/app/Livewire/Admin/Finance.php b/app/Livewire/Admin/Finance.php
new file mode 100644
index 0000000..3d71dcc
--- /dev/null
+++ b/app/Livewire/Admin/Finance.php
@@ -0,0 +1,124 @@
+<?php
+
+namespace App\Livewire\Admin;
+
+use App\Models\InvoiceSeries;
+use App\Support\CompanyProfile;
+use App\Support\Settings;
+use Illuminate\Support\Facades\Storage;
+use Livewire\Attributes\Layout;
+use Livewire\Component;
+use Livewire\WithFileUploads;
+
+/**
+ * Everything an invoice needs before one can be issued.
+ *
+ * Its own tab rather than a section of Settings: the company's registered
+ * details, the VAT rate and the Rechnungskreise are not preferences, they are
+ * what appears on a legal document, and burying them under "Einstellungen"
+ * beside the site-visibility switch invites somebody to change one in passing.
+ *
+ * None of it reaches an invoice that already exists. Every value is copied into
+ * the invoice when its number is assigned, so an address corrected here is
+ * correct from the next document onwards and cannot rewrite an old one.
+ */
+#[Layout('layouts.admin')]
+class Finance extends Component
+{
+    use WithFileUploads;
+
+    /** @var array<string, mixed> */
+    public array $company = [];
+
+    public float $taxRate = 20.0;
+
+    /** New logo upload, validated on save. */
+    public $logo = null;
+
+    public string $logoPath = '';
+
+    public function mount(): void
+    {
+        $this->authorize('site.manage');
+
+        $this->company = CompanyProfile::all();
+        $this->logoPath = (string) ($this->company['logo_path'] ?? '');
+        $this->taxRate = CompanyProfile::taxRate();
+    }
+
+    public function saveCompany(): void
+    {
+        $this->authorize('site.manage');
+
+        $data = $this->validate([
+            'company.name' => 'required|string|max:190',
+            'company.address' => 'required|string|max:190',
+            'company.postcode' => 'required|string|max:20',
+            'company.city' => 'required|string|max:120',
+            'company.country' => 'required|string|max:120',
+            'company.phone' => 'nullable|string|max:60',
+            'company.email' => 'nullable|email|max:190',
+            'company.website' => 'nullable|string|max:190',
+            'company.register_number' => 'nullable|string|max:60',
+            'company.register_court' => 'nullable|string|max:120',
+            'company.vat_id' => 'required|string|max:40',
+            'company.bank_name' => 'nullable|string|max:120',
+            'company.iban' => 'nullable|string|max:42',
+            'company.bic' => 'nullable|string|max:15',
+            'company.payment_days' => 'required|integer|min:0|max:180',
+            'company.payment_terms' => 'nullable|string|max:500',
+            // PNG or WEBP only, and small. A PDF embeds whatever it is given,
+            // and a four-megabyte photograph would be embedded in every invoice
+            // ever rendered from then on.
+            'logo' => 'nullable|image|mimes:png,webp|max:1024',
+            'taxRate' => 'required|numeric|min:0|max:100',
+        ]);
+
+        if ($this->logo !== null) {
+            $previous = $this->logoPath;
+
+            $this->logoPath = $this->logo->store('company', 'public');
+            $this->company['logo_path'] = $this->logoPath;
+
+            // The old file goes only once the new one is stored. The other
+            // order loses the logo entirely if the upload fails, and every
+            // invoice rendered afterwards is missing it.
+            if ($previous !== '' && $previous !== $this->logoPath) {
+                Storage::disk('public')->delete($previous);
+            }
+
+            $this->logo = null;
+        }
+
+        CompanyProfile::put($data['company']);
+        Settings::set('company.tax_rate', (float) $data['taxRate']);
+
+        $this->dispatch('notify', message: __('finance.company_saved'));
+    }
+
+    public function removeLogo(): void
+    {
+        $this->authorize('site.manage');
+
+        if ($this->logoPath !== '') {
+            Storage::disk('public')->delete($this->logoPath);
+        }
+
+        $this->logoPath = '';
+        $this->company['logo_path'] = '';
+        CompanyProfile::put(['logo_path' => '']);
+
+        $this->dispatch('notify', message: __('finance.logo_removed'));
+    }
+
+    public function render()
+    {
+        return view('livewire.admin.finance', [
+            'series' => InvoiceSeries::query()->orderBy('kind')->get(),
+            // What is still missing before an invoice may be issued at all. An
+            // invoice without a name, an address or a VAT number is not a valid
+            // invoice here, and issuing one is worse than refusing to.
+            'missing' => CompanyProfile::missingForInvoicing(),
+        ]);
+    }
+}
diff --git a/app/Support/CompanyProfile.php b/app/Support/CompanyProfile.php
new file mode 100644
index 0000000..3cf12ee
--- /dev/null
+++ b/app/Support/CompanyProfile.php
@@ -0,0 +1,103 @@
+<?php
+
+namespace App\Support;
+
+/**
+ * Who is issuing the invoice.
+ *
+ * Every field a printed invoice needs, kept in settings rather than in config,
+ * because an operator has to be able to change an address without a deployment
+ * — and because the values are copied into each invoice at issue anyway, so
+ * changing one here never rewrites a document that already exists.
+ *
+ * A typed front door onto Settings rather than string keys scattered through
+ * views and PDF code: there are fifteen of them, an invoice is a legal
+ * document, and a typo in a key silently prints an empty line where the VAT
+ * number belongs.
+ */
+final class CompanyProfile
+{
+    private const PREFIX = 'company.';
+
+    /** Every key, with its default. The list IS the schema. */
+    public const FIELDS = [
+        'name' => '',
+        'address' => '',
+        'postcode' => '',
+        'city' => '',
+        'country' => 'Österreich',
+        'phone' => '',
+        'email' => '',
+        'website' => '',
+        // Firmenbuch / commercial register, and the court that keeps it.
+        'register_number' => '',
+        'register_court' => '',
+        // UID / VAT identification number — the one field an invoice is
+        // legally worthless without.
+        'vat_id' => '',
+        'bank_name' => '',
+        'iban' => '',
+        'bic' => '',
+        'logo_path' => '',
+        // Payment terms in days, and the sentence printed under the total.
+        'payment_days' => 14,
+        'payment_terms' => '',
+    ];
+
+    /** @return array<string, mixed> */
+    public static function all(): array
+    {
+        $values = [];
+
+        foreach (self::FIELDS as $key => $default) {
+            $values[$key] = Settings::get(self::PREFIX.$key, $default);
+        }
+
+        return $values;
+    }
+
+    public static function get(string $field, mixed $default = null): mixed
+    {
+        return Settings::get(self::PREFIX.$field, $default ?? (self::FIELDS[$field] ?? null));
+    }
+
+    /** @param array<string, mixed> $values */
+    public static function put(array $values): void
+    {
+        foreach ($values as $key => $value) {
+            // Unknown keys are dropped rather than stored. This is fed from a
+            // form, and a forged field must not be able to write an arbitrary
+            // setting into the same table the site-visibility switch lives in.
+            if (! array_key_exists($key, self::FIELDS)) {
+                continue;
+            }
+
+            Settings::set(self::PREFIX.$key, $value);
+        }
+    }
+
+    /**
+     * Is there enough here to put on an invoice?
+     *
+     * Not a nicety: an invoice without a company name, an address or a VAT
+     * number is not a valid invoice in Austria, and issuing one is worse than
+     * refusing to. The console asks this before it offers the button.
+     *
+     * @return array<int, string> the fields that are missing, empty when ready
+     */
+    public static function missingForInvoicing(): array
+    {
+        $required = ['name', 'address', 'postcode', 'city', 'vat_id'];
+
+        return array_values(array_filter(
+            $required,
+            fn (string $field) => trim((string) self::get($field)) === '',
+        ));
+    }
+
+    /** The VAT rate as a percentage, e.g. 20.0. */
+    public static function taxRate(): float
+    {
+        return (float) Settings::get('company.tax_rate', 20.0);
+    }
+}
diff --git a/app/Support/Navigation.php b/app/Support/Navigation.php
index 0f3df14..d3a01c4 100644
--- a/app/Support/Navigation.php
+++ b/app/Support/Navigation.php
@@ -50,6 +50,10 @@ final class Navigation
                 ['admin.maintenance', 'alert-triangle', 'maintenance', null],
                 ['admin.vpn', 'shield', 'vpn', null],
                 ['admin.revenue', 'trending-up', 'revenue', null],
+                // Its own entry, not a section of Settings: what is set here
+                // appears on a legal document, and burying it beside the
+                // site-visibility switch invites somebody to change one in passing.
+                ['admin.finance', 'receipt', 'finance', 'site.manage'],
             ]],
             ['label' => __('admin.nav_group.system'), 'items' => [
                 ['admin.mail', 'mail', 'mail', 'mail.manage'],
diff --git a/lang/de/admin.php b/lang/de/admin.php
index d17f508..0f45efe 100644
--- a/lang/de/admin.php
+++ b/lang/de/admin.php
@@ -20,6 +20,7 @@ return [
         'provisioning' => 'Provisioning',
         'maintenance' => 'Wartungen',
         'vpn' => 'VPN',
+        'finance' => 'Finanzen',
         'revenue' => 'Umsatz',
         'mail' => 'E-Mail',
         'secrets' => 'Zugangsdaten',
diff --git a/lang/de/finance.php b/lang/de/finance.php
new file mode 100644
index 0000000..9525323
--- /dev/null
+++ b/lang/de/finance.php
@@ -0,0 +1,69 @@
+<?php
+
+return [
+    'title' => 'Finanzen',
+    'subtitle' => 'Firmendaten für die Rechnung, Steuersatz und Rechnungskreise.',
+
+    // Was fehlt, bevor überhaupt etwas ausgestellt werden darf. Eine Rechnung
+    // ohne Namen, Anschrift oder UID ist keine gültige Rechnung — sie
+    // auszustellen ist schlimmer, als es zu verweigern.
+    'incomplete' => 'Es fehlen noch Angaben, ohne die keine Rechnung ausgestellt werden kann: :fields',
+
+    'company_title' => 'Firmendaten',
+    'company_sub' => 'Diese Angaben stehen im Kopf und in der Fußzeile jeder Rechnung. Eine Änderung gilt ab der nächsten Rechnung — bereits ausgestellte behalten den Stand, unter dem sie ausgestellt wurden.',
+    'company_saved' => 'Firmendaten gespeichert.',
+    'save' => 'Speichern',
+    'logo_remove' => 'Logo entfernen',
+    'logo_removed' => 'Logo entfernt.',
+
+    'field' => [
+        'name' => 'Firmenwortlaut',
+        'address' => 'Straße und Hausnummer',
+        'postcode' => 'PLZ',
+        'city' => 'Ort',
+        'country' => 'Land',
+        'phone' => 'Telefon',
+        'email' => 'E-Mail',
+        'website' => 'Website',
+        'register_number' => 'Firmenbuchnummer',
+        'register_court' => 'Firmenbuchgericht',
+        'vat_id' => 'UID-Nummer',
+        'bank_name' => 'Bank',
+        'iban' => 'IBAN',
+        'bic' => 'BIC',
+        'logo' => 'Logo',
+        'tax_rate' => 'Umsatzsteuer (%)',
+        'payment_days' => 'Zahlungsziel (Tage)',
+        'payment_terms' => 'Zahlungsbedingungen',
+    ],
+
+    'hint' => [
+        'vat_id' => 'Pflichtangabe auf jeder Rechnung.',
+        'tax_rate' => 'Wird in jede Rechnung eingefroren. Eine Änderung wirkt nur auf neue Rechnungen.',
+        'logo' => 'PNG oder WEBP, höchstens 1 MB. Wird in jede erzeugte Rechnung eingebettet.',
+    ],
+
+    'series_edit_title' => 'Rechnungskreis bearbeiten',
+    'series_saved' => 'Rechnungskreis gespeichert.',
+    'series_locked' => 'Nicht mehr änderbar: :n Dokument(e) tragen dieses Kürzel bereits in ihrer Nummer.',
+    'series_floor' => 'Kann nur erhöht werden. Eine niedrigere Nummer wäre schon vergeben — mindestens :n.',
+    'cancel' => 'Abbrechen',
+
+    'series_title' => 'Rechnungskreise',
+    'series_sub' => 'Jeder Kreis hat sein eigenes Kürzel und seinen eigenen lückenlosen Zähler. Eine Gutschrift ist keine Rechnung mit Minus davor.',
+    'series' => [
+        'name' => 'Bezeichnung',
+        'prefix' => 'Kürzel',
+        'next' => 'Nächste Nummer',
+        'reset' => 'Zähler',
+        'reset_yearly' => 'jährlich neu',
+        'reset_never' => 'fortlaufend',
+        'actions' => 'Aktionen',
+        'digits' => 'Stellen',
+        'reset_label' => 'Zähler jedes Jahr neu beginnen',
+        'reset_hint' => 'Dann steht das Jahr in der Nummer: RE-2026-0001. Nach dem ersten Dokument nicht mehr änderbar.',
+        'active_label' => 'Für neue Dokumente verwendbar',
+        'active_hint' => 'Abgeschaltet bleibt alles Bestehende erhalten, es wird nur nichts Neues mehr daraus ausgestellt.',
+        'edit' => 'Bearbeiten',
+    ],
+];
diff --git a/lang/en/admin.php b/lang/en/admin.php
index b058726..413ae6f 100644
--- a/lang/en/admin.php
+++ b/lang/en/admin.php
@@ -20,6 +20,7 @@ return [
         'provisioning' => 'Provisioning',
         'maintenance' => 'Maintenance',
         'vpn' => 'VPN',
+        'finance' => 'Finance',
         'revenue' => 'Revenue',
         'mail' => 'Email',
         'secrets' => 'Credentials',
diff --git a/lang/en/finance.php b/lang/en/finance.php
new file mode 100644
index 0000000..cf29cf5
--- /dev/null
+++ b/lang/en/finance.php
@@ -0,0 +1,69 @@
+<?php
+
+return [
+    'title' => 'Finance',
+    'subtitle' => 'Company details for invoices, the VAT rate, and the invoice series.',
+
+    // What is missing before anything may be issued. An invoice without a name,
+    // an address or a VAT number is not a valid invoice — issuing one is worse
+    // than refusing to.
+    'incomplete' => 'Some details are still missing, and no invoice can be issued without them: :fields',
+
+    'company_title' => 'Company details',
+    'company_sub' => 'These appear in the header and footer of every invoice. A change applies from the next invoice onwards — anything already issued keeps the details it was issued under.',
+    'company_saved' => 'Company details saved.',
+    'save' => 'Save',
+    'logo_remove' => 'Remove logo',
+    'logo_removed' => 'Logo removed.',
+
+    'field' => [
+        'name' => 'Registered name',
+        'address' => 'Street and number',
+        'postcode' => 'Postcode',
+        'city' => 'City',
+        'country' => 'Country',
+        'phone' => 'Phone',
+        'email' => 'Email',
+        'website' => 'Website',
+        'register_number' => 'Register number',
+        'register_court' => 'Registering court',
+        'vat_id' => 'VAT ID',
+        'bank_name' => 'Bank',
+        'iban' => 'IBAN',
+        'bic' => 'BIC',
+        'logo' => 'Logo',
+        'tax_rate' => 'VAT (%)',
+        'payment_days' => 'Payment terms (days)',
+        'payment_terms' => 'Payment conditions',
+    ],
+
+    'hint' => [
+        'vat_id' => 'Required on every invoice.',
+        'tax_rate' => 'Frozen into every invoice. A change affects new invoices only.',
+        'logo' => 'PNG or WEBP, 1 MB at most. Embedded into every invoice rendered.',
+    ],
+
+    'series_edit_title' => 'Edit invoice series',
+    'series_saved' => 'Invoice series saved.',
+    'series_locked' => 'No longer editable: :n document(s) already carry this prefix in their number.',
+    'series_floor' => 'Can only be raised. A lower number has already been issued — at least :n.',
+    'cancel' => 'Cancel',
+
+    'series_title' => 'Invoice series',
+    'series_sub' => 'Each series keeps its own prefix and its own gapless counter. A credit note is not an invoice with a minus sign in front of it.',
+    'series' => [
+        'name' => 'Name',
+        'prefix' => 'Prefix',
+        'next' => 'Next number',
+        'reset' => 'Counter',
+        'reset_yearly' => 'restarts yearly',
+        'reset_never' => 'continuous',
+        'actions' => 'Actions',
+        'digits' => 'Digits',
+        'reset_label' => 'Restart the counter each year',
+        'reset_hint' => 'The year then appears in the number: RE-2026-0001. Not editable once a document has been issued.',
+        'active_label' => 'Available for new documents',
+        'active_hint' => 'Switched off, everything already issued stays; only nothing new is issued from it.',
+        'edit' => 'Edit',
+    ],
+];
diff --git a/resources/views/livewire/admin/edit-invoice-series.blade.php b/resources/views/livewire/admin/edit-invoice-series.blade.php
new file mode 100644
index 0000000..02ba45c
--- /dev/null
+++ b/resources/views/livewire/admin/edit-invoice-series.blade.php
@@ -0,0 +1,54 @@
+<div class="rounded-lg bg-surface p-6">
+    <div class="flex items-center justify-between">
+        <h3 class="text-base font-semibold text-ink">{{ __('finance.series_edit_title') }}</h3>
+        <span class="rounded bg-surface-2 px-2 py-0.5 font-mono text-xs text-muted">{{ $prefix }}</span>
+    </div>
+
+    <div class="mt-4 space-y-4">
+        <x-ui.input name="name" wire:model="name" :label="__('finance.series.name')" />
+
+        {{-- Editable only while nothing has been issued. The prefix is part of
+             every number already on a document: changing it renames nothing and
+             leaves a series whose past says RE and whose future says AR. --}}
+        <div>
+            <label class="text-sm font-medium text-body" for="series-prefix">{{ __('finance.series.prefix') }}</label>
+            @if ($issued === 0)
+                <input id="series-prefix" type="text" wire:model="prefix"
+                       class="mt-1.5 w-full rounded-md border border-line-strong bg-surface px-3 py-2 font-mono text-sm uppercase text-ink" />
+            @else
+                <input id="series-prefix" type="text" value="{{ $prefix }}" disabled
+                       class="mt-1.5 w-full cursor-not-allowed rounded-md border border-line bg-surface-2 px-3 py-2 font-mono text-sm text-muted" />
+                <p class="mt-1 text-xs text-muted">{{ __('finance.series_locked', ['n' => $issued]) }}</p>
+            @endif
+            @error('prefix')<p class="mt-1 text-xs text-danger">{{ $message }}</p>@enderror
+        </div>
+
+        <div class="grid gap-4 sm:grid-cols-2">
+            <x-ui.input name="digits" wire:model="digits" type="number" :label="__('finance.series.digits')" />
+            <div>
+                <label class="text-sm font-medium text-body" for="series-next">{{ __('finance.series.next') }}</label>
+                <input id="series-next" type="number" min="{{ $floor }}" wire:model="nextNumber"
+                       class="mt-1.5 w-full rounded-md border border-line-strong bg-surface px-3 py-2 font-mono text-sm text-ink" />
+                <p class="mt-1 text-xs text-muted">{{ __('finance.series_floor', ['n' => $floor]) }}</p>
+                @error('nextNumber')<p class="mt-1 text-xs text-danger">{{ $message }}</p>@enderror
+            </div>
+        </div>
+
+        @if ($issued === 0)
+            <div class="rounded-lg border border-line bg-surface-2 p-4">
+                <x-ui.checkbox name="yearlyReset" wire:model="yearlyReset" :label="__('finance.series.reset_label')" />
+                <p class="mt-1.5 pl-7 text-xs text-muted">{{ __('finance.series.reset_hint') }}</p>
+            </div>
+        @endif
+
+        <div class="rounded-lg border border-line bg-surface-2 p-4">
+            <x-ui.checkbox name="active" wire:model="active" :label="__('finance.series.active_label')" />
+            <p class="mt-1.5 pl-7 text-xs text-muted">{{ __('finance.series.active_hint') }}</p>
+        </div>
+    </div>
+
+    <div class="mt-6 flex justify-end gap-3">
+        <x-ui.button variant="secondary" x-on:click="Livewire.dispatch('closeModal')">{{ __('finance.cancel') }}</x-ui.button>
+        <x-ui.button variant="primary" wire:click="save" wire:loading.attr="disabled">{{ __('finance.save') }}</x-ui.button>
+    </div>
+</div>
diff --git a/resources/views/livewire/admin/finance.blade.php b/resources/views/livewire/admin/finance.blade.php
new file mode 100644
index 0000000..9615b83
--- /dev/null
+++ b/resources/views/livewire/admin/finance.blade.php
@@ -0,0 +1,125 @@
+<div class="space-y-5">
+    <div class="animate-rise">
+        <h1 class="text-2xl font-bold tracking-tight text-ink">{{ __('finance.title') }}</h1>
+        <p class="mt-1 text-sm text-muted">{{ __('finance.subtitle') }}</p>
+    </div>
+
+    {{-- What is still missing before anything may be issued. An invoice without
+         a name, an address or a VAT number is not a valid invoice, and issuing
+         one is worse than refusing to. --}}
+    @if ($missing !== [])
+        <x-ui.alert variant="warning" class="animate-rise">
+            {{ __('finance.incomplete', ['fields' => collect($missing)->map(fn ($f) => __('finance.field.'.$f))->join(', ')]) }}
+        </x-ui.alert>
+    @endif
+
+    <form wire:submit="saveCompany" class="space-y-5 rounded-lg border border-line bg-surface p-6 shadow-xs animate-rise [animation-delay:60ms]">
+        <div>
+            <h2 class="font-semibold text-ink">{{ __('finance.company_title') }}</h2>
+            <p class="mt-1 max-w-2xl text-sm text-muted">{{ __('finance.company_sub') }}</p>
+        </div>
+
+        <div class="grid gap-4 sm:grid-cols-2">
+            <x-ui.input name="company.name" wire:model="company.name" :label="__('finance.field.name')" class="sm:col-span-2" />
+            <x-ui.input name="company.address" wire:model="company.address" :label="__('finance.field.address')" class="sm:col-span-2" />
+            <x-ui.input name="company.postcode" wire:model="company.postcode" :label="__('finance.field.postcode')" />
+            <x-ui.input name="company.city" wire:model="company.city" :label="__('finance.field.city')" />
+            <x-ui.input name="company.country" wire:model="company.country" :label="__('finance.field.country')" />
+            <x-ui.input name="company.phone" wire:model="company.phone" :label="__('finance.field.phone')" />
+            <x-ui.input name="company.email" wire:model="company.email" :label="__('finance.field.email')" />
+            <x-ui.input name="company.website" wire:model="company.website" :label="__('finance.field.website')" />
+        </div>
+
+        <div class="grid gap-4 border-t border-line pt-5 sm:grid-cols-2">
+            <x-ui.input name="company.vat_id" wire:model="company.vat_id" :label="__('finance.field.vat_id')" :hint="__('finance.hint.vat_id')" placeholder="ATU12345678" />
+            <x-ui.input name="company.register_number" wire:model="company.register_number" :label="__('finance.field.register_number')" placeholder="FN 123456a" />
+            <x-ui.input name="company.register_court" wire:model="company.register_court" :label="__('finance.field.register_court')" placeholder="Handelsgericht Wien" />
+            <div>
+                <label class="text-sm font-medium text-body" for="tax-rate">{{ __('finance.field.tax_rate') }}</label>
+                <input id="tax-rate" type="number" step="0.1" min="0" max="100" wire:model="taxRate"
+                       class="mt-1.5 w-full rounded-md border border-line-strong bg-surface px-3 py-2 font-mono text-sm text-ink" />
+                <p class="mt-1 text-xs text-muted">{{ __('finance.hint.tax_rate') }}</p>
+                @error('taxRate')<p class="mt-1 text-xs text-danger">{{ $message }}</p>@enderror
+            </div>
+        </div>
+
+        <div class="grid gap-4 border-t border-line pt-5 sm:grid-cols-3">
+            <x-ui.input name="company.bank_name" wire:model="company.bank_name" :label="__('finance.field.bank_name')" />
+            <x-ui.input name="company.iban" wire:model="company.iban" :label="__('finance.field.iban')" />
+            <x-ui.input name="company.bic" wire:model="company.bic" :label="__('finance.field.bic')" />
+        </div>
+
+        <div class="grid gap-4 border-t border-line pt-5 sm:grid-cols-3">
+            <x-ui.input name="company.payment_days" wire:model="company.payment_days" type="number" :label="__('finance.field.payment_days')" />
+            <x-ui.input name="company.payment_terms" wire:model="company.payment_terms" :label="__('finance.field.payment_terms')" class="sm:col-span-2" />
+        </div>
+
+        {{-- The logo. Replaceable, because a company changes its mark and every
+             invoice rendered after that has to carry the new one — while every
+             invoice already issued keeps the one it was issued with, because
+             the path is copied into the document at issue. --}}
+        <div class="border-t border-line pt-5">
+            <label class="text-sm font-medium text-body">{{ __('finance.field.logo') }}</label>
+            <div class="mt-2 flex flex-wrap items-center gap-4">
+                <div class="grid size-20 place-items-center overflow-hidden rounded-lg border border-line bg-surface-2">
+                    @if ($logo)
+                        <img src="{{ $logo->temporaryUrl() }}" alt="" class="max-h-16 max-w-16 object-contain" />
+                    @elseif ($logoPath)
+                        <img src="{{ Storage::disk('public')->url($logoPath) }}" alt="" class="max-h-16 max-w-16 object-contain" />
+                    @else
+                        <x-ui.icon name="receipt" class="size-6 text-muted" />
+                    @endif
+                </div>
+                <div class="min-w-0">
+                    <input type="file" wire:model="logo" accept="image/png,image/webp"
+                           class="block w-full text-sm text-body file:mr-3 file:rounded-md file:border file:border-line-strong file:bg-surface-2 file:px-3 file:py-1.5 file:text-sm file:text-body" />
+                    <p class="mt-1 text-xs text-muted">{{ __('finance.hint.logo') }}</p>
+                    @error('logo')<p class="mt-1 text-xs text-danger">{{ $message }}</p>@enderror
+                    @if ($logoPath)
+                        <button type="button" wire:click="removeLogo" class="mt-2 text-xs font-medium text-danger underline">{{ __('finance.logo_remove') }}</button>
+                    @endif
+                </div>
+            </div>
+        </div>
+
+        <div class="flex justify-end border-t border-line pt-5">
+            <x-ui.button variant="primary" type="submit" wire:loading.attr="disabled">{{ __('finance.save') }}</x-ui.button>
+        </div>
+    </form>
+
+    {{-- The Rechnungskreise. Each has its own prefix and its own gapless
+         counter — a credit note is not an invoice with a minus sign. --}}
+    <div class="overflow-hidden rounded-lg border border-line bg-surface shadow-xs animate-rise [animation-delay:90ms]">
+        <div class="border-b border-line p-6">
+            <h2 class="font-semibold text-ink">{{ __('finance.series_title') }}</h2>
+            <p class="mt-1 max-w-2xl text-sm text-muted">{{ __('finance.series_sub') }}</p>
+        </div>
+        <table class="w-full text-sm">
+            <thead>
+                <tr class="border-b border-line bg-surface-2 text-left text-xs font-semibold text-muted">
+                    <th class="px-4 py-3 font-semibold">{{ __('finance.series.name') }}</th>
+                    <th class="px-4 py-3 font-semibold">{{ __('finance.series.prefix') }}</th>
+                    <th class="px-4 py-3 font-semibold">{{ __('finance.series.next') }}</th>
+                    <th class="px-4 py-3 font-semibold">{{ __('finance.series.reset') }}</th>
+                    <th class="px-4 py-3 text-right font-semibold">{{ __('finance.series.actions') }}</th>
+                </tr>
+            </thead>
+            <tbody>
+                @foreach ($series as $row)
+                    <tr wire:key="series-{{ $row->uuid }}" class="border-b border-line last:border-0">
+                        <td class="px-4 py-3 text-body">{{ $row->name }}</td>
+                        <td class="px-4 py-3 font-mono font-semibold text-ink">{{ $row->prefix }}</td>
+                        <td class="px-4 py-3 font-mono text-xs text-muted">{{ str_pad((string) $row->next_number, $row->digits, '0', STR_PAD_LEFT) }}</td>
+                        <td class="px-4 py-3 text-xs text-muted">{{ $row->yearly_reset ? __('finance.series.reset_yearly') : __('finance.series.reset_never') }}</td>
+                        <td class="px-4 py-3 text-right">
+                            <x-ui.button variant="secondary"
+                                         x-on:click="$dispatch('openModal', { component: 'admin.edit-invoice-series', arguments: { uuid: '{{ $row->uuid }}' } })">
+                                {{ __('finance.series.edit') }}
+                            </x-ui.button>
+                        </td>
+                    </tr>
+                @endforeach
+            </tbody>
+        </table>
+    </div>
+</div>
diff --git a/routes/admin.php b/routes/admin.php
index 598a933..0945b67 100644
--- a/routes/admin.php
+++ b/routes/admin.php
@@ -38,6 +38,7 @@ Route::get('/provisioning', Admin\Provisioning::class)->name('provisioning');
 Route::get('/maintenance', Admin\Maintenance::class)->name('maintenance');
 Route::get('/vpn', Admin\Vpn::class)->name('vpn');
 Route::get('/revenue', Admin\Revenue::class)->name('revenue');
+Route::get('/finance', Admin\Finance::class)->name('finance');
 Route::get('/mail', Admin\Mail::class)->name('mail');
 Route::get('/secrets', Admin\Secrets::class)->name('secrets');
 Route::get('/infrastructure', Admin\Infrastructure::class)->name('infrastructure');
diff --git a/tests/Feature/Billing/FinanceSettingsTest.php b/tests/Feature/Billing/FinanceSettingsTest.php
new file mode 100644
index 0000000..badef37
--- /dev/null
+++ b/tests/Feature/Billing/FinanceSettingsTest.php
@@ -0,0 +1,134 @@
+<?php
+
+use App\Livewire\Admin\EditInvoiceSeries;
+use App\Livewire\Admin\Finance;
+use App\Models\Invoice;
+use App\Models\InvoiceSeries;
+use App\Support\CompanyProfile;
+use Livewire\Livewire;
+
+/**
+ * The details that end up on a legal document, and the parts of an invoice
+ * series that stop being editable once one has been issued.
+ */
+it('refuses to consider itself ready without the fields an invoice legally needs', function () {
+    // An invoice without a name, an address or a VAT number is not a valid
+    // invoice in Austria. Issuing one is worse than refusing to.
+    expect(CompanyProfile::missingForInvoicing())
+        ->toContain('name')->toContain('address')->toContain('vat_id');
+
+    CompanyProfile::put([
+        'name' => 'CluPilot Cloud e.U.',
+        'address' => 'Musterstraße 1',
+        'postcode' => '1010',
+        'city' => 'Wien',
+        'vat_id' => 'ATU12345678',
+    ]);
+
+    expect(CompanyProfile::missingForInvoicing())->toBe([]);
+});
+
+it('stores the company details from the finance tab', function () {
+    Livewire::actingAs(operator('Owner'), 'operator')
+        ->test(Finance::class)
+        ->set('company.name', 'CluPilot Cloud e.U.')
+        ->set('company.address', 'Musterstraße 1')
+        ->set('company.postcode', '1010')
+        ->set('company.city', 'Wien')
+        ->set('company.country', 'Österreich')
+        ->set('company.vat_id', 'ATU12345678')
+        ->set('company.payment_days', 14)
+        ->set('taxRate', 20)
+        ->call('saveCompany')
+        ->assertHasNoErrors();
+
+    expect(CompanyProfile::get('vat_id'))->toBe('ATU12345678')
+        ->and(CompanyProfile::taxRate())->toBe(20.0);
+});
+
+it('drops a field that is not part of the profile', function () {
+    // This is fed from a form. A forged key must not be able to write an
+    // arbitrary setting into the same table the site-visibility switch uses.
+    CompanyProfile::put(['site.public' => false, 'name' => 'Echt']);
+
+    expect(App\Support\Settings::get('site.public', true))->toBeTrue()
+        ->and(CompanyProfile::get('name'))->toBe('Echt');
+});
+
+it('lets a series be renamed and its prefix corrected while nothing has been issued', function () {
+    $series = InvoiceSeries::query()->where('kind', 'invoice')->firstOrFail();
+
+    Livewire::actingAs(operator('Owner'), 'operator')
+        ->test(EditInvoiceSeries::class, ['uuid' => $series->uuid])
+        ->set('name', 'Ausgangsrechnung')
+        ->set('prefix', 'ar')
+        ->call('save')
+        ->assertHasNoErrors();
+
+    expect($series->refresh()->prefix)->toBe('AR')
+        ->and($series->name)->toBe('Ausgangsrechnung');
+});
+
+it('freezes the prefix once a document carries it', function () {
+    // The prefix is part of every number already issued. Changing it renames
+    // nothing and leaves a series whose past says RE and whose future says AR.
+    $series = InvoiceSeries::query()->where('kind', 'invoice')->firstOrFail();
+    issueOne($series);
+
+    Livewire::actingAs(operator('Owner'), 'operator')
+        ->test(EditInvoiceSeries::class, ['uuid' => $series->uuid])
+        ->set('prefix', 'AR')
+        ->set('name', 'Ausgangsrechnung')
+        ->call('save')
+        ->assertHasNoErrors();
+
+    expect($series->refresh()->prefix)->toBe('RE')
+        // The rest of the form still saves.
+        ->and($series->name)->toBe('Ausgangsrechnung');
+});
+
+it('will not let the counter be wound back onto a number already issued', function () {
+    // Gapless AND ascending. A lower number is one that is already printed on
+    // a document somebody holds.
+    $series = InvoiceSeries::query()->where('kind', 'invoice')->firstOrFail();
+    $series->update(['next_number' => 25]);
+
+    Livewire::actingAs(operator('Owner'), 'operator')
+        ->test(EditInvoiceSeries::class, ['uuid' => $series->uuid])
+        ->set('nextNumber', 7)
+        ->call('save')
+        ->assertHasErrors(['nextNumber']);
+
+    expect($series->refresh()->next_number)->toBe(25);
+});
+
+it('does let the counter be moved forward', function () {
+    // Skipping numbers is lawful — reusing them is not. An operator migrating
+    // from another system needs exactly this.
+    $series = InvoiceSeries::query()->where('kind', 'invoice')->firstOrFail();
+
+    Livewire::actingAs(operator('Owner'), 'operator')
+        ->test(EditInvoiceSeries::class, ['uuid' => $series->uuid])
+        ->set('nextNumber', 500)
+        ->call('save')
+        ->assertHasNoErrors();
+
+    expect($series->refresh()->next_number)->toBe(500);
+});
+
+/** A minimal issued document, enough to make a series non-empty. */
+function issueOne(InvoiceSeries $series): Invoice
+{
+    return Invoice::create([
+        'invoice_series_id' => $series->id,
+        'number' => $series->prefix.'-2026-0001',
+        'number_year' => 2026,
+        'number_sequence' => 1,
+        'issued_on' => now()->toDateString(),
+        'snapshot' => ['issuer' => [], 'lines' => []],
+        'net_cents' => 1900,
+        'tax_cents' => 380,
+        'gross_cents' => 2280,
+        'currency' => 'EUR',
+    ]);
+}